A need exists for relatively low cost optical fibers to connect components in applications such as office intranets and the like. Such applications may be referred to as "fiber to the desktop" or "FTTD" applications. Some of the issues faced or desired system criteria if optical fibers are to replace existing connectors such as copper wires, coaxial cable and the like are ease of manufacture, ease of connection, relatively low cost for run lengths which typically will not exceed 500 m, low attenuation, preferably less than 10 dB/km, and high bandwidth, preferably greater than 500 MHz-km at both 850 and 130 nm.
Some efforts have been made to develop multicore plastic optical fibers. While such fibers are both inexpensive and relatively large so that they can be relatively easily connected, they suffer from poor performance characteristics, such as low bandwidth, high attenuation, possible environmental constraints because plastic will burn and high temperatures will deform the fiber core geometry altering the optical characteristics, and short link lengths, typically 50 m or less. Efforts have also been made to utilize multimode glass optical fibers in FTTD applications. While such fibers meet some of the presently perceived needs, such fibers are still relatively costly and not optimally matched to these applications.
Additionally, some efforts have been made to manufacture multiple core optical fibers, see, for example, EPO 193 921 in the name of Sumitomo Electric Industries published Sep. 10, 1986 and U.S. Pat. No. 4,561,871 assigned to the assignee of the present invention and incorporated by reference herein in its entirety. These approaches involve forming or boring holes in a preform and inserting rods into those holes. As such, they do not have the ease of manufacture or low costs desired for many applications as the hole boring and inserting steps tend to be relatively time consuming and complex tasks which are not readily applicable to forming a fiber with a large plurality of cores, such as eight or more.
While the above discussion addresses several of the presently desired system criteria for FTTD applications, it will be recognized both that other criteria may apply and that a wide variety of applications are ripe for a low cost multicore optical fiber having the properties of the fibers according to the present invention and designed to advantageously address the needs of such applications.